Professor Dorothy Crawford takes us on a virus hunt.

Dorothy H. Crawford has been Assistant Principal for Public Understanding of Medicine at the University of Edinburgh since 2007. She is author of the forthcoming book, VIRUS HUNT (Oxford, August 2013). Her previous books include The Invisible Enemy, Deadly Companions, and Viruses: A Very Short Introduction.

From hospital intensive care wards to research laboratories to the African rain forests, Crawford follows the trail of the virus back to its roots deep in Africa. We track wild monkeys and apes through the jungle–gathering their DNA via hair and feces samples–to discover from which primates HIV first jumped to our species, ultimately concluding that the most virulent strain, HIV-1, came from chimpanzees in Cameroon. We then time travel back to colonial Africa around the turn of the 20th century, when the virus first spread to humans. But even the rapidly mutating HIV could not survive in one person long enough to adapt to our immune system. Crawford shows that it may have been given the opportunity to adapt by being transmitted rapidly from one person to the next through unsterile syringes, ironically used during a campaign to wipe out disease by mass inoculation. The book then moves to Leopoldville (now Kinshasa), where Crawford describes the unique series of social upheavals, starting in the 1920s, that sparked epidemic levels of sexually transmitted diseases, allowed HIV-1 to begin its exponential growth. And when in the 1960s chance took the virus abroad to Haiti, from where it jumped to the United States, its pandemic spread began.

Crawford tells a gripping story of brilliant scientific sleuthing, breakthrough discoveries, tragic errors, stubborn intractable mysteries, generous collaborations, and bitter disputes. And along the way, she conveys, with a light and engaging touch, a wealth of interesting observations about viruses, DNA, disease, immune systems, the very latest research methods, and of course HIV.

 

1. Could you briefly explain what HIV is and how it leads to the detriment of the immune system?

As a virus HIV is one of the most destructive. This is because it targets the very cells in the body that are meant to protect us.  These are CD4 lymphocytes that play a pivotal role in immunity against viruses. HIV is a retrovirus.  The hallmark of this virus family is that when they infect a cell they convert their RNA into DNA which then integrates into the cell’s DNA. By doing this the virus’s genome becomes part of the cell’s genome and can be carried for life in a latent state unrecognised by the immune system.  When the virus replicates it kills the cell in which it is lodging.  In an infected person HIV destroys millions of CD4 lymphocytes every day and eventually these cells can no longer be replaced and their numbers drop.  The body is then unable to fight off other microbes and opportunistic infections ensue. It is these infections that finally kill the host.

2. Could you tell us about your research interests?

My research is on Epstein-Barr virus (EBV). My next book after Virus Hunt is about EBV (Cancer Virus) and will be launched next year on the 50^th anniversary of the discovery of EBV. I won’t give too much away at this stage, but EBV is a cancer-causing virus associated with several different types of tumours including Burkitt lymphoma, lymphoma in immune suppressed patients and some cases of Hodgkin lymphoma.  Recently I have been working on immunotherapy – that is harnessing the immune response to the virus to treat the tumours it causes. We have succeeded in curing cases of EBV lymphomas in immune suppressed transplant recipients using EBV specific killer T lymphocytes harvested from healthy blood donors.

3. In your book; The invisible enemy : A natural history of viruses there is a sense of awe and fascination at the biological wonders of viruses. In your opinion, what is the most fascinating aspect of viruses?

To me the most fascinating thing about viruses is the fact that they are so small and yet so powerful.  There 100 million different types of viruses and they are the most abundant life form in the oceans with up to 10 billion of them per litre!

4. Viruses have also attracted the attention of mathematicians for their unique geometries and surface chemistry. In addition to this, artists are often inspired by viruses, perhaps because they are considered to be beautiful but deadly. Are there any situations where viruses may act symbiotically with the human body or do all viruses cause us harm?

Not all viruses are harmful to us or other animals. In fact there are many in the environment which infect and kill bacteria and algae thereby controlling their numbers. This is obviously essential to maintain the balance of nature.  Similarly we are just beginning to understand the role of bacterial flora on and inside our bodies and again viruses are there maintaining a stable population of the bacteria.

5.Could you briefly explain the ‘Bushmeat’ theory of the origin of HIV?

The work that I describe in Virus Hunt clearly identifies the direst ancestor of HIV as the simian immunodeficiency virus (SIV) carried by one subspecies of chimpanzee that live in the rain forests of Cameroon.  There has been much debate about how the virus transferred from chimps to humans but the most likely scenario is referred to as the ‘cut-hunter’ or ‘natural-transmission’ theory.  This theory proposes that since in Cameroon chimps are hunted for food and SIV is a blood borne virus, it transferred from hunted to hunter during the bloody process of capturing and butchering an animal.

6. Do you think we will ever be able to safely exploit the features of viruses for Gene therapy?

Viruses are used in gene therapy as a convenient way of getting foreign DNA into cells. All their ‘dangerous’ genes are removed and so the risk to the patient should be very small.  There have been some initial problems using this approach but gene therapy is getting safer all the time so I think that using a virus as a DNA delivery system will turn out to be just as safe and any other method.

7. In your opinion, who will be the final victor – man or microbe?

There won’t be a final victor in the dual between man and microbes. The struggle will continue and become ever more sophisticated.  Microbes mutate very quickly and so have the advantage of rapid adaptation.  On the other hand humans have technology on their side which can hopefully fill the gap while our immune system slowly catches up.  This is the continuing arms race that has been going on for thousands of years.

8. What are your views on, Berkeley Virologist, Peter Duesberg’s theory that HIV is a harmless passenger virus? Does this claim have any validity?

The claim that HIV is a harmless virus is frankly wrong. Although the theory had some validity in the 1980s the link between HIV infection and AIDS has now been proved to everyone’s satisfaction except Peter Duesberg and his few followers.

9. Most readers of this blog are medical students. What sort of information could they learn from your latest book Virus Hunt that may not be emphasised at medical school?

Virus Hunt is written as a detective story.  It follows the research that reveals how, when, where and why HIV infected humans and then spread globally. Beginning in the US where AIDS was first recognised in the early 1980s, it jumps to Europe where HIV was discovered and then to Africa where the epidemic was already out of control.  The story gives a fascinating insight into the international scientific collaborations that eventually uncovered the answers by involving skilled teams of experts as diverse as medical doctors, veterinary surgeons, field ecologists, molecular biologists, geneticists and epidemiologists.